These touch fastener elements also include mechanical fastening elements, with touch fastener elements made in a complementary manner, form a fastener which can be repeatedly opened and closed. Hooks or mushroom-like fastener parts interacting with loop-like fastener elements of another touch fastener element with the formation of a touch or a touch-and-close fastener. Solutions are also known in which the same touch fastener elements of two different touch fastener elements interact with one another (hermaphroditic fastener).
DE 699 22 264 T2 discloses supplying a belt-like backing part with a plurality of projecting stem parts to a molding gap between heatable molding rolls. An extrusion means supplies an additional molding belt of plastic material into the gap as the actual molding tool with mold recesses shapes the hot stem ends of the stem parts into head parts to form a mushroom-like touch fastener element. Since the head parts in the known solution are formed from the plastic material of the stem parts, the head parts are of smaller dimension due to low material charging in the free and projecting head surface available for interlocking. This smaller dimension can adversely affect the required adhesion forces.
Conversely, U.S. Pat. No. 6,180,205 proposes a production method using a molding roll in which a belt-like backing part can be connected to a plurality of hook fastener elements dimensioned to be relatively large. For this purpose, the molding roll on its outer periphery has hook-shaped mold recesses into which plastic material is pressed to fill the mold a first extruder. Excess plastic material on the outer peripheral side of the molding roll is removed by cutting removal means, technically called a doctor blade. By a second extruder located downstream in the production direction, the backing part material is then applied and permanently connected to the hook-shaped fastener parts during the cooling process of the roll. A stripper roll then removes the finished fastener part from the molding means. Due to the hook geometry, difficulties can arise during the mold removal process. Furthermore, a relatively high proportion of plastic scrap is formed in the production process due to use of the doctor blade.
WO 2006/099000 A2 discloses spraying a belt-like conveyor device on its upper strand side with droplets of plastic material. The plastic material is molded based on its surface tension into hemispherical shell bodies which are then permanently connected on their arching top to a belt-like backing part, with the formation of a touch fastener element. In one development of this solution it is also possible, in the manner of thickened stem parts, to supply a belt-like backing part which on its top bears grain-shaped agglomerates as the stem parts onto which then the hemispherical head parts can be placed. The touch fastener element produced in this way and designed to be used in particular as a fastener for baby diapers or incontinence diapers is, however, made relatively stiff and leaves much to be desired with respect to the fastener characteristics. U.S. Patent Publication 2006/0220271 A1 discloses a comparable solution calling for a molding tool in the form of a molding roll with the corresponding mold recesses instead of a belt for production of hemispherical fastener elements. Production of stem parts between the head parts and backing part is not done with this known solution.
U.S. Pat. No. 5,785,784 discloses a production method for producing a belt-like backing part on which a plurality of projecting stem parts extend. In a downstream production step, the free stem ends are heated and then thicken as a result of the surface tension of the plastic material, in particular, into a hemispherical head part. If, in a continuation of the known solution, the head parts produced in this way are reshaped by a calander rolling method, widened head part geometries are formed which, with respect to the low material charge, are made relatively small and are widened only in the rolling direction.